Flexible wave guide



DEC. 14, 1954 R s, vvCARR 2,696,834

` FLEXIBLE WAVE GUIDE Filed May ll, 1949 INVENTOR ATTORNEYS UnitedStates Patent O .FLEXIBLE WAVE GUIDE Roberts. (Carr, 'Maplewood, N. J.,assigner to Airtron, Inc.,'Linden, N. J., acorporation of New JerseyApplication May `11, 1949, :Serial No. 92,640

-Claims. Cl. 13S-56) 'This *invention relates lto improvements `inlfiex'ib'le waveguides .and 1more particularly to waveguides which are:suitable for being subjected internally to fluid pressure--andtotcontain such pressure to enhance `the conduction characteristicsof :the waveguide.

Waveguides, as :referred to fherein, are ordinarilyem- -ployed :for thepurpose of transmitting micro-waves in radar and ftelevision equipmentand in :other equipment in which electrical impulses, usually of highfrequency, 4are prcsentand :require conduction between `variouscomponents of the apparatus. Under many `conditions Eit :.is necessaryor vdesirable to provide waveguides which are iflexible, :to -perrnitlimited vmovement or vibration :of .various parts of such apparatusrelatively to eachother `or rto Ypermit `contortion of the waveguide tofacilitate its .installation inthe apparatus.

It has 'been lfound that waveguides should perefabht be :hollow `andrectangular in cross section, and `to meet ythese Arequirements while`nevertheless providing 'for vilexibility'in'the waveguide,'it hasbecome more or less conventional practice to form Vthe :guiding or condating portionfofthe waveguide of hollow, thin metal tubing ofrectangular -cross section vhaving yperipherally extending .corrugationsto impart flexibility to the tubing. {Such ,flexible tubing can beproduced in various ways as, for example, by -merelv ypressing suchcorrugations iinto a previously formed more or less rigid tubingor bywinding Ia llongitudinally convoluted strip of thin, .lilexible `metalspirally-upon a rectangular mandrel insuch a way that the convolutionsof each turn of thestrip -aboutthe ,mandrel interlock with eachpreceding and succeeding turn, thereby forming a continuous tube. informing the guidingor-conducting core of the waveguide inlhealatter.mannen it is desirable to solder Lthe-spiralseam sothat thereris `noairleakage through/or slippage in `said seam; l.the Vflexibility of themetal in -the convolutions being .relied upon .to rvgive therequisiteexibility to the hollow,

.tubularvcore 'Sometimes the solder is zomitted yfrom 4the seam vso.that ,ma ycertain amount of slippage vis present therein. While thismay enhance `the flexibility -of ythe waveguide to some extent, it hasbeen found that itdoes .not Iyield best `results from `the standpoint,of microvwave guidance or conduction.

A .complete waveguide includes suitable `connecting iilangesorecuivalent connecting means ixed ,tothe oppo- `site ends 'of a length ofsuch a hollow, trnetal, 'tubular core and commonly is provided with an`outerjacliet of rubber, synthetic rubber .or other rubber-.likematerial.

It ,has .been found that waveguides :are much ymore .efficient for.micro-wave guiding `and `conduction purposes, yif .the waveguides and`other parts of a wave .conduction system are maintained Vwith y.duidpressure `there- "in substantially ygreater than atmospheric pressure.lpresent .invention comorehends :improvements inflexible waveguideswhich enable them to .contain `ailuid suchas air .under pressure,thereby ,rendering them suitable for use in such pressurized systems.

`lt an important'obiect of the present {invention to provide waveguideswhich yare adequately vilexible 'but which `nevertl'ieless have thecapacity of ,containing yair `under substantial `pressure withoutmaterial leakage.

.Another important obiect of this invention'is vthe .provision of,.allexible waveguide in which ,connecting danger at one xor bothendsthereof are adapted .forlirm aixar-.tiou ,to the metalconductingcore ofthe waveguide and are grooved peripheraliy `to afford auidiight interlock lwith a rubberlikeiaclret which covers the said core.

.Another .important ,object Lis .the Lprovision, in a ilexiblewaveguide, .of -means 1to1-preventing material outice ward fdistortionfor bulging rof `the metal conducting core as a result t ofrsubstant'ial fair pressure therewithin, Awhile nevertheless ipreservingsubstantial ilexibility yin the core.

Another object of .this :invention is the yprovision of a;lexible.waveguidehaving means `for preventing material :outwardtdistortion orVbulgingof the metal conducting core in the tpresence of substantialypressure therewitlinand having connecting `flanges or their equivalentLrrnly.andfluicbtightly fixed atopposite ends of the said core, .and:improved `means aifording an interlocking, fluid-tight connection,between lsuch `flanges -and a -frubberlike `jacket providedias 1acovering forthe core.

The foregoing :and ,other .objects of this `invention should .beapparent from the ,following description ,and `the Aaccompanying drawingrin which:

vFigure vl is aside .elevational view, partly in central axial isection,of a tllexible waveguide according to .the 4present invention;

Fig. 2 .is a cross-sectional view atfone hanged end of the saidwaveguide,ithesection.being-substantially on the .line ',2-2 `of .-Fig.q1.;

.Fig. ,3 isa.cros s sectional viewatone flanged end of the saidwaveguide, .the t section lbeing lsubstantially on t the -lineSw-.S ofg'Fig. .1;

Fig. `4 is a view toward `one send -of .a Amodified form of waveguideaccording to this invention, the said View beingtpartly in `sideelevation and partly in central axial section, `and fbeingrbroken `awayinlayers to show certain interior `parts `in .side elevation;

Fig. 5:is a vieu/.substantially like-thefleft side of Fig. l, .showing:a -further Amodified `form of vflexible waveguide .accordingto .this`invention;` and .16 ,isa view substantially like Fig 4 4but `showinguthermoditication within the present invention. to Figs. .l-.3,inclusive, the .flexible waveguide illustrated therein fcomprises .aflexible, metal, tubular `core .11, `which fis `rectangular in `crosssection and is :shown ashavingplural peripheral .corrugations or con-,volutions 12 suitableQforimparting.exibility to said core. As .theIparticular.conformation o'f `the convolutions and Vthemanncr of'forming them do notion-a any essential ,part ,of this invention, suchconvolutions are shown Vin thefdrawing onlydiagrammatically rather Vthanin detail. flthoughlit is considered preferable that themetal, tubularcorefbe convoluted, nevertheless it should he under fstocd that ,the@present invention valso comprehends .flexjible 'waveguides which mayhave other structural ,provisions -for yielding exibility as, forexample, an .unsoldered tslip joint or seam between turns ofinterlocking, non-.convoluted strip metal.

Connectionelementsin the form of connecting anges 13 `preferablyareuid-tightly fixed upon the core 11 at ,the `ends ,of ,theilatter asby soldering at 14, yto afford means forconnecting the waveguides toother pieces of equipment; and a ljacket 15 of relatively soft rubber,,syntheticrubber or other rubber-like ilexible material is :suitablylmolded in place `to completely surround the `portion ,of Vthecore'between the `said connecting flanges. The 'liacket V`1'5 conformsin outer shape to the core l2.

having a wall .of substantially uniform thickness except ,as notedhereafter.

The connectinganges 13, 4as illustrated, have a main or 'bodyportion 16with bolt holes 17 therein to receive bolts `for `inter-ccnnecting thelwaveguide between other pieces of equipment. Although similar `flangesare illustrated at Aopposite ends of the waveguide, 'it is, of course,Within thepresent "inventionto provide diferent 'flanges or equivalentconnecting means at opposite ends yof the waveguide, ,andmeans otherthanboltsmay be employed -to effect connection with other pieces ,ofequipment. For this reason such `.connecting flanges or other suitablemeans 'for .inter-connecting the waveguide with other V,equipment l,are:sometimes referred to herein ,and 4in the claims `asconnection-,elements.

Asbest seen in lFig. l, the ,connection element .13 has.anfinterlockingportion .1.5, integral with the bodylportion .316, andextending therefrom in a ,generallyrlongitudinal or axial direction..The :interlocking portion 18 vis formed with a .continuous .inner:peripheral groove 19 :adjacent to ...the fbody portion .51,6, .and acontinuous .outer peripheral gtoovetoward .the..free.end ofsaid.interlockingportiou 'I'he provision of the mentioned grooves givesthe interlocking portion 18 a somewhat zigzag or convoluted shape asviewed in axial section as it appears in Fig. 1. The interlockingportion thus consists of an outer longitudinally extending web 21, atransverse or radial web 22 which connects the web 21 to an innerlongitudinally extending web 23, and a transverse or radial flange 24which extends outwardly from the web 23.

It may be observed that the inner diameters of the web 23 are greaterthan the corresponding outer diameters of the flexible metal core 11, sothat when the jacket 15 is molded to constitute a part of the device,the rubberlike material of that jacket extends between the web 23 andthe core 11 and extends into and completely fills the inner peripheralgroove 19. Also, it may be observed that the outer diameters of theradial flanges 24 are less than the corresponding outer diameters of theweb 21, so that when the jacket 15 is molded in place, the rubber-likematerial thereof completely encases the flange 24 and extends into andcompletely fills the outer peripheral groove 2l). Under the lastmentioned conditions the rubber-like material of the jacket may beformed to give it outer diameters at the connection element which arethe same as the corresponding outer diameters of the web 21, so that theadjacent outer surfaces of the said web and of the jacket are in effectcontinuous uninterrupted surfaces; the rubber-like material of thejacket being smoothly graduated from the connection element into themain body portion of the jacket without any undesirable lumps or ridges.

It may be seen that under the above described arrangement there exists alrm mechanical and fluid-tight interlock between the jacket 15 and theconnection element 13. It should be appreciated that, although theflexible metal core may be made to be air-tight, it may neverthelessdevelop slight leaks which would enable fluid pressure to escape fromwithin the core. If this occurs and if the pressure within the waveguideis not extremely high, the jacket 15 should prevent the escape of airand thus maintain the pressure within the waveguide. In this condition,however, the described interlocking arrangement between the jacket 15and the connection elements 13 is of considerable importance; forwithout it, air leaking from within the core 11 would passlongitudinally between the latter and the jacket 15 and would eventuallyfind avenues of escape at the ends of the jacket. However, with aninterlocking arrangement as herein described, air attempting to escapewould have to pass completely around the rubber-like material within thegroove 19, thence completely around the web 23 and the radial flange 24,and thence around the rubber-like material within the groove 2t).

There are several features about the described interlocking arrangementwhich operate to prevent such escape of fluid under pressure. Forexample, the molding of the jacket 15 to the remainder of the waveguidecauses the rubber-like material of the jacket to extend within the innergroove 19 and in the space between the web 23 and the core 11 and causesthose spaces to be completely filled with the rubber-like material tothereby oppose the escape of air therethrough. In addition, if airshould find its way to a point between the interlocking portion 18 andthe convolutions of the metal core 11 underlying that interlockingportion, the air pressure at that point would deform the rubber-likematerial outwardly, thus urging it very tightly into the groove 19 andinto an enhanced sealing engagement with the outer surface of the web23, so that the pressure of the air itself aids in preventing the escapeof the air at the end of the jacket.

Aside from the effect of air pressure as just described for preventingthe escape of air, it is obvious that for air to escape at the end ofthe jacket, it must pursue a circuitous and lengthy path, and this initself presents very substantial opposition to its possible escape.

The embodiment of this invention shown in Fig. 4 differs from thatillustrated in Figs. 1-3, inclusive, only in the addition of a sheath 2Sof braided metal wire or braided thin metal strip material whichpreferably is braided upon and extends entirely about the metal core 11.The metal of which this sheath is formed preferably is somewhat flexibleand of suflicient tensile strength to permit flexing of the core 11while nevertheless preventing any material outward bulging thereof inthe presence of fluid pressure therewithin. The soldering at 14, to fixthe connection element 13 upon the core, permeates the braided sheath inthe vicinity of the said element so that the solder, in addition toserving as a means of aflixing the flange to the core, also serves, asin the first described embodiment, to prevent the escape of fluidpressure between the element 13 and the core 11. In the structureillustrated in Fig. 4, the interlocking portion 18 functions similarlyto its counterpart, as previously described with reference to Figs. 1-3.

The structure illustrated in Fig. 5 differs from that illustrated inFigs. 1 3 only in that its connection element, instead of having bothinner and outer grooves such as grooves l@ and 20 of Fig. l, is providedwith only an outer groove 20a. In this arrangement, the soldering at 14prevents the escape of fluid pressure between the connecting flange 13aand the metal core 11, and fluid pressure attempting to escape at theend of the jacket 15 would have to find its way around the radial flange24 and thence around the rubber-like material of the jacket which fillsthe outer groove 20a. However, if air pressure should find its wayaround the radial flange 24 and to the inner radial face of said flange,the pressure of the air at that point would tend to urge the rubber-likematerial in the groove Zita leftwardly as viewed in Fig. 5, therebyenhancing its sealing contact with the left radial surface which definesthe said groove; thus in this structure, as in that of Figs. 1 4, theair pressure itself aids in sealing against its escape.

The structure illustrated in Fig. 6 is similar to that illustrated inFig. 5, except that it includes also a braided metal sheath 25. Thissheath is like its counterpart in the structure in Fig. 4, and functionssimilarly thereto, and the connecting flange 13a is similar to andfunctions similarly to its counterpart illustrated in Fig. 5.

it should be apparent from the foregoing that by providing connectionelement or flange structures and a fluidtight rubber-like jacket havingits end portions interlocked with such elements or flanges according tothis invention, a very effective means is provided for preventing theescape of fluid pressure from a flexible waveguide; and that flexiblewaveguides according to this invention may be pressurized to containfluid pressures substantially above atmospheric pressure and thereby berendered more efflcient for the conduction of micro-wave energy. Itshould also be apparent that the provision of the braided metal sheath,as hereinbefore described, affords suitable means for preventing anymaterial radial distortion of the flexible metal core which mightundesirably alter the conduction characteristics of the waveguide.

Although the capacity of the herein disclosed waveguides to containfluid pressure is limited to pressures which are not sufficiently highto cause ballooning or bursting of the rubber-like jacket, it shouldnevertheless be obvious that waveguides according to this invention maybe adapted for containing higher fluid pressures by the simple expedientof providing a jacket which is sufficiently stronger to enable it towithstand the higher pressures.

It should be understood that the present inventive concept may beembodied in various structures other than those hereinbefore describedand illustrated in the accompanying drawings, without, however,departing from the invention as set forth in the following claims.

What I claim is:

l. A flexible waveguide comprising an approximately rectangular,flexible, tubular, conductive inner core which is substantiallyresistant to the passage of fluid from the interior to the exteriorthereof; a connection element fluid-tightly fixed to said core towardone end thereof and having an approximately rectangular inner-endportion with a substantially continuous, peripherally extending,radially opening groove therein having approximately parallel sidewalls;and a flexible, fluid impervious, tubular jacket, which is approximatelyrectangular throughout its length, surrounding said core and extendinginto lapping relationship relatively to said inner-end portion of theconnection element with the material of said jacket extending into andsubstantially filling said groove to oppose passage of fluid between theconnection element and the jacket; the jacket material in and borderingsaid groove being in substantially non-flexed condition, whereby suchmaterial in said groove is free of any flexing influence from suchbordering material tending to loosen the said material from its fillingposition in the groove, said connection element further having a secondsuch groove with the jacket material extending therento and filling it,one of said grooves opening radially outwardly and the other of saidgrooves opening radially inwardly.

2. A exible waveguide comprising an approximately rectangular, flexible,tubular, conductive inner core which is substantially resistant to thepassage of fluid from the interior to the exterior thereof; a connectionelement Huid-tightly fixed to said core toward one end thereof andhaving an approximately rectangular inner-end portion with asubstantially continuous, peripherally extending, radially openinggroove therein having approximately parallel sidewalls; and a exible,fluid impervious, tubular jacket, which is approximately rectangularthroughout its length, surrounding said core and extending into lappingrelationship relatively to said inner-end portion of the connectionelement with the material of said jacket extending into andsubstantially filling said groove to oppose passage of uid between theconnection element and the jacket; the jacket material in and borderingsaid groove being in substantially non-flexed condition, whereby suchmaterial in said groove is free of any flexing influence from suchbordering material tending to loosen the said material from its fillingposition in the groove, said core further being formed with peripherallyextending corrugations and the material of said jacket extending intoand lling said corrugations.

3. A exible waveguide comprising the combination of a substantiallyrectangular, flexible, tubular, fluidtight metallic inner core, ametallic, rigid connection element having a longitudinal openingtherethrough to receive said core, an end of said core being inserted insaid opening and said core being fluid-tightly connected to saidconnection element, said connection element further comprisingintegrally an outer web extending longitudinally inwardly of said core,a web integral with said outer web and extending radially inwardlytherefrom, an inner web integral with said radial web and extendingtherefrom longitudinally inwardly of said core and in spaced relationthereto, and a flange integral with said inner web and extendingradially outwardly therefrom and terminating radially inwardly of saidouter web, said webs and flange defining a radially inwardly open grooveand a radially outwardly open groove, and said waveguide furthercomprising a flexible, fluid impervious tubular jacket molded aroundsaid core and in said grooves and filling the latter, said jacketfurther comprising a body portion having a wall of substantially uniformthickness and conforming in outer diameter to said outer web and beingsmoothly graduated therefrom into said body portion.

4. A exible waveguide according to claim 2, further including a exiblesheath which is substantially nonexpansible peripherally, intimatelysurrounding the said core and restraining the latter against peripheralexpansion in the presence of fluid pressure therewithin.

5. A iiexible waveguide according to claim 1, further characterized inthat the said connection element has a body portion extending around thecore toward one end thereof and an integral, peripherally continuousweb, of S-shape in longitudinal section, extending longitudinallyinwardly and being embedded within said jacket material with thereversely extending parts of the S deining the mentioned grooves; thesaid web, longitudinally inwardly of the mentioned inwardly-openinggroove being of greater internal diameter than the corresponding outerdiameter of the said core to provide space for accommodating the jacketmaterial uninterruptedly from the body portion of the jacket to and intothe said inwardly-opening groove, and said jacket material extendinguninterruptedly from the body portion of the jacket to and into the saidoutwardly-opening groove.

6. A flexible waveguide according to claim 1, further including a exiblesheath of relatively high tensile strength, intimately surrounding thesaid core and restraining the latter against peripheral enlargement inthe presence of fluid pressure therewithin.

References Cited in the file of this patent UNITED STATES PATENTS NumberName Date 1,461,130 Loughead July 10, 1923 1,630,895` Herbst May 31,1927 1,684,717 Sherbino Sept. 18, 1928 1,847,218 Lamb Mar. 1, 19322,085,563 Aime June 29, 1937 2,257,355 Vohrer Sept. 30, 1941 2,261,948Beach Nov. 11, 1941 2,308,073 Hagerty Jan. 12, 1943 2,467,036 IftigerApr. 12, 1949 2,479,288 Allen Aug. 16, 1949 OTHER REFERENCES MicrowaveTransmission Circuits, Radiation Laboratory SerieS-Ragan-Published May28, 1948.

C. Q. Magazine-The Radio Amateurs Journal-November 1946 issue- Page 25.

